1. Field of the Invention
The present invention relates to a material for extrusion molding and a process for preparation of molding products therefrom. More particularly, it is concerned with a material for extrusion molding, a process for preparation thereof, and a process for preparing molded articles therefrom, such as fiber, nonwoven fabric, film, sheet, tube, rod, and bottle.
2. Description of the Related Arts
The general purpose styrene-based polymer which is produced by conventional radical polymerization etc., has an atactic configuration and is amorphous. However, the polystyrene having an atactic configuration, being used in various fields, has poor heat resistance and solvent resistance, therefore an improvement of these characteristics is required.
Since the styrene-based polymer having a high degree of syndiotactic configuration which the present inventors' group developed previously has a high melting point, a high crystallization rate, an excellent heat resistance and an excellent chemical resistance, it is expected to be used in various fields. Consequently, it was proposed that the styrene-based polymer having a high degree of syndiotactic configuration is used for stretched film, sheet, yarn, fiber, nonwoven fabric (Japanese Patent Application Laid-Open No. 182346/1989 etc.) The above products are expected to be obtained by continuous molding by melt extrusion. In the molding process, a styrene-based polymer having a high degree of syndiotactic configuration or a composition containing the styrene-based polymer are fed as pellet for the raw material. The suggestion of this pellet was not disclosed previously. Pellets that have been pelletized by a conventional method have the problems described below.
When these pellets are heated to a temperature above the glass transition temperature thereof, the pellets easily adhere to one another to form an agglomerate in the feed zone of the extruder, or adhere to the screw and the inner wall of barrel of the extruder. As a result, pellets are not fed smoothly, or when they are heated in the hopper before feeding into the extruder, the adhering pellets form an agglomerate at the exit of the hopper, and accordingly the continuous molding is sometimes hindered. When pellets are not fed smoothly, the retention time in melting is prolonged, an offensive odor is caused by the decomposition of the polymer. In addition, the appearance and physical properties of the products become poor due to foaming caused in molding, whereby the products are not suitable for practical use. Even when pellets are molded without such problems, products with a poor appearance caused by melt fracture are occasionally observed.
Therefore, the present inventors group have made intensive studies to solve the problems described above and provide a material for extrusion molding to be an excellent extrusion product with good appearance and physical properties in a stable continuous process, together with a process for preparation thereof and a process for preparing the molding products.